Switched to Apache2 license, added README, removed useless file.

Is everybody okay with this? As far as I'm aware, AdvDuplicator's license wasn't discussed, but this is necessary for the workshop. There are some other people we need to ping, @Kadah (formerly TAD2020) is the principal author, @AT-Kenny and has also contributed code to this repository but not agreed to the Wiremod license change.